1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a method of driving a plasma display panel.
2. Description of the Background Art
Generally, a plasma display panel (hereinafter abbreviated PDP) displays an image including characters and graphics in a manner of exciting a fluorescent substance by a 147 nm UV-ray emitted from a mixed gas discharge of (He+Xe), (Ne+Xe), or (He+Ne+Xe). PDP provides an excellent quality of image due to the recent development of technology as well as can be provided with a slim size and wide-screen. Specifically, a 3-electrodes AC surface discharge type PDP lowers its voltage necessary for an electric discharge using wall charges accumulated on a surface and protects its electrodes from sputtering occurring on the electric discharge, thereby being advantageous in enabling a low voltage drive and long endurance.
FIG. 1 is a perspective diagram of a discharge cell of a 3-electrodes AC surface discharge type PDP according to a related art. Referring to FIG. 1, a discharge cell of a 3-electrodes AC surface discharge type PDP consists of a scan electrode 30Y and sustain electrode 30Z formed on an upper substrate 10 and an address electrode 20X formed on a lower substrate 18.
Each of the scan and sustain electrodes 30Y and 30Z has a line width smaller than that of a transparent electrode 12Y or 12Z and includes a metal bus electrode 13Y or 13Z. The transparent electrodes 12Y and 12Z are generally formed of indium tin oxide (ITO) on the upper substrate 10. The metal bus electrodes 13Y and 13Z are generally formed of metal such as Cr or the like on the transparent electrodes 12Y and 12Z to reduce the voltage drops caused by the transparent electrodes 12Y and 12Z of high resistance, respectively. An upper dielectric layer 14 and protecting layer 16 are stacked over the upper substrate 10 including the scan and sustain electrodes 30Y and 30Z. Wall charges generated from plasma discharge are accumulated on the upper dielectric layer 14. The protecting layer 16 protects the upper dielectric layer 14 against sputtering caused by plasma discharge and increases discharge efficiency of secondary electrons. And, the protecting layer 16 is generally formed of MgO.
The address electrode 20X is formed in a direction crossing with that of the scan or sustain electrode 30Y or 30Z. A lower dielectric layer 22 and barrier rib 24 are formed on the lower substrate 8, having the address electrode 20X formed thereon. A fluorescent layer 26 is formed on surfaces of the lower dielectric layer 22 and the barrier rib 24. The barrier rib 24 is formed parallel to the address electrode 20Z to physically partition each discharge cell and prevents UV and visible rays generated from electric discharge from leaking to neighbor discharge cells. The fluorescent layer 26 is excited by the UV-ray generated from plasma discharge to emit light including one of red, green, and blue visible rays. A mixed inert gas such as He+Xe, Ne+Xe, He+Xe+Ne, and the like for electric discharge is injected in a discharge space of the discharge cell provided between the barrier ribs 24 and the upper and lower substrates 10 and 18.
In the above-configured 3-electrodes AC surface discharge type PDP, one frame is divided into several sub-fields differing in luminous times to implement gray levels. And, each of the sub-fields is divided again into a reset period for arousing electric discharge evenly, an address period for selecting a discharge cell, and a sustain period for implementing gray levels according to a discharging number.
For instance, in case of displaying an image at 256 gray levels, a frame period (16.67ms) corresponding to 1/60 second is divided into eight sub-fields SF1 To SF8. And, each of the eight sub-fields SF1 to SF8 is divided into a reset period, an address period, and a sustain period. The reset and address periods of the respective sub-fields are equal to each other, whereas the sustain periods and their discharge numbers of the respective sub-fields increase at a ratio of 2n (n=0, 1, 2, 3, 4, 5, 6, 7), respectively. As the sustain period varies according to the corresponding sub-field, the image gray levels can be implemented.
Substantially, the sub-fields of the frame are selected to implement the gray levels in a manner of Table 1.
TABLE 1SF1SF2SF3SF4SF5SF6SF7SF8Y1Y2Y3Y8Y16Y32Y64Y1280XXXXXXXX1◯XXXXXXX2X◯XXXXXX15◯◯◯◯XXXX16XXXX◯XXX17◯XXX◯XXX31◯◯◯◯◯XXX32XXXXX◯XX33◯XXXX◯XX63◯◯◯◯◯◯XX64XXXXXX◯X127◯◯◯◯◯◯◯X128XXXXXXX◯255◯◯◯◯◯◯◯◯
In Table 1, ‘SFx’ means an xth sub-field, ‘Yz’ indicates a brightness weight set to a decimal number for the corresponding sub-field, ‘O ’ indicates a turned-on state of the corresponding sub-field, and ‘x’ indicates a turned-off state of the corresponding sub-field.
The sub-fields, as shown in Table 1, bring about sustain discharges to correspond to the brightness weights allocated to them, respectively, thereby representing gray levels corresponding to the brightness weights, respectively. Yet, in the related art sub-field driving method, a discharge error may occur in the gray levels 15-16, 31-32, 63-64, and 127-128 where luminous patterns are varied more considerably than those of the previous gray levels, respectively. Moreover, in the gray levels 15-16, 31-32, 63-64, and 127-128 where luminous patterns are greatly varied, it is difficult to control wall charges.
Specifically, in order to represent the gray level of ‘31’, the sustain discharge occurs in the first to fifth sub-fields SF1 to SF5. In doing so, since a plurality of the sub-fields are selected from one frame to represent the gray level of ‘31’, the address discharge can occur stably in the selected sub-fields. In other words, the address discharge occurring in the fifth sub-field SF5 can take place stably due to the priming discharged particles produced from the previous sub-fields.
In order to represent the gray level of ‘32’, the sustain discharge takes place in the sixth sub-field SF6. In doing so, one sub-field is selected from one frame to represent the gray level of ‘32’. In other words, the address discharge occurring in the sixth sub-field SF6 should take place without the aid of charged particles produced from the previous sub-field. For such a reason, it is highly probable that the address discharge may fail in the sixth sub-field SF6.
Meanwhile, in another related art, 10% Ne—Xe at 46 kPa is set as the discharge gas sealed within the PDP to increase density of the Xe component. Thus, even if a drive voltage of the high-density Xe panel becomes higher than that of the related art low-density Xe panel, brightness can be enhanced. Hence, the high-density Xe panel enables to display an image of high brightness by raising the Xe component of the discharge gas. Yet, since the drive voltage of the high-density Xe panel is set higher than that of the low-density Xe panel, it becomes more probable that the discharge failure of the high-density Xe panel may occur in the gray levels of 15-16, 31-32, 63-64, and 127-128 of which luminous patterns are varied more considerably than those of the previous gray levels, respectively.